1. Field of the Invention
This invention pertains, in general, to lighting devices for keyswitch assemblies and keyboards, such as computer desktop, laptop, and notebook keyboards or xe2x80x9cInternet-TVxe2x80x9d keyboards. More specifically, the invention relates to backlighting for keyboards that originates from below the keys within the keyboard.
2. Related Art
For a long time, keyswitch assembly operators have desired lighted keyboards and keypads. For example, when an operator is working a computer keyboard and simultaneously viewing a computer monitor, low ambient light conditions may be preferred, in order to maximize contrast on the monitor screen. Also, for example, a portable computer operator may by necessity be in a low light environment, as when flying in an airplane or riding in a train at night.
In any event, there have been many attempts in the prior art to provide lighted keyboards and keypads. Still, many of these attempts have not been successful because they result in keyswitch assemblies that are not sufficiently lighted, or lighted in a glaring or distracting manner, or that are inconvenient, or expensive. Prior attempts at lighted keyboards have produced fragile systems that consume more power and produce more heat than is desirable.
Examples of lighted keyswitch assemblies are found in the patent literature. U.S. Pat. No. 5,801,345 (Mikula-Curtis et al., 1998) discloses LED""s attached to the bottom of the printed circuit board (PCB) which emit light that travels up through holes in the PCB and into light pipes, each of which is received in a key cap to channel the light up through the interior of the key cap. Also, the Mikula-Curtis et al. system includes a backlighting system with an LED centered under a light dam and an indicia panel, that emits light up through the center of the area enclosed by the light dam to back-light the indicia panel.
U.S. Pat. No. 5,612,692 (Dugas et al., 1997) discloses a sealed, LED-lighted keyboard, in which the LEDs are disposed on the printed circuit board. The LEDs and circuit board are covered by a spacer board with openings for allowing electrical contact with the top surface of the circuit board and for allowing LED light to reach the upper layers of the system. These xe2x80x9cupper layersxe2x80x9d include a translucent sealing sheet membrane with domes, and keys above the domes. Thus, in Dugas, the keys are pushed down to force the domes down so that a conductive under-surface of the key may contact the circuit board. The LED light must travel up through the spacer board holes, through the center of each dome, up through the center of each key, and out the translucent number, letter, or other indicia on the top center of the key cap.
U.S. Pat. No. 5,034,602 (Garcia, et al., 1991) discloses a backlighting system in which a light emitter, such as an alpha/numeric LED or LCD, is disposed beneath the center of the key cap or adjacent to a beam splitter that redirects the light up through the central axis of the key cap.
U.S. Pat. No. 4,806,908 (Krupnik, 1989) discloses a system using electroluminescent (EL) strips that extend through registering openings that extend transversely through the stems of the key switches in the keyboard. The EL strips extend from key stem to key stem underneath an opaque, stationary retaining panel being between the keys, so that only the key cap is lit only by light that is emitted from the area of the EL strips inside the key stems (the xe2x80x9cinternal portionxe2x80x9d) and that travels up to the cap of the key. This light from the internal portion of the EL strip travels up through the center of the clear, transparent, or translucent body of the key stem and then to openings or translucent areas in the center of the otherwise opaque key cap. Because the EL strips run underneath the opaque retaining panel and through openings in the stems of a plurality of keys, the EL strips are also adapted to prevent withdrawal of the keys from the retaining panel.
Summarily, therefore, conventional backlighting techniques feature means for channeling/directing light directly up through the center of the key cap or of the area directly under the indicia panel to be lit. This approach purposely controls the light to travel along a specific central axis and then to radiate from the keyboard in a limited area of a single key cap or of a single indicia panel. This approach purposely controls and limits the light path, to prevent light from traveling from keyswitch to keyswitch or from shining from the inside of the keyswitch to the outside of the keyswitch.
What is still needed is a durable, economical and effective backlighting system for a desktop, laptop, notebook, or xe2x80x9cInternet-TVxe2x80x9d keyboard. What is needed is such a system that supplies appropriate levels of light in the appropriate areas of the keyboard for enhanced viewing in low/no light environments.
The present invention comprises lighting a keyboard for use in low or no ambient light environments, by peripherally lighting the keyswitch assemblies on a keyboard or keypad, such as a desktop, laptop, notebook, or Internet-TV keyboard. By xe2x80x9cperipherally lighted,xe2x80x9d it is meant that the keyswitch assemblies are lit externally, from outside rather than from inside, preferably from positions substantially circumscribing the sides and/or extending across the bottom of the keyswitch assemblies. Light emanates from all or portions of a panel that extends between and/or underneath a plurality of keyswitches of a keyboard. The panel may be a sheet or strip that extends between keyswitches and preferably reaches underneath the keycaps, by extending near to the stem or stem path of a keyswitch, and/or by extending underneath the keyswitches. Preferably, light emanates up from the radiant panel through the spaces between the keyswitches, and into and through the keyswitches, to give the selected portions of the keyboard an overall xe2x80x9cglowingxe2x80x9d appearance, rather than giving the keyboard the appearance of having xe2x80x9cspotsxe2x80x9d of light or lighted letters and numerals. This lighting aids key identification and overall visibility in many low/no light environments, and makes laptop lighting possible while traveling because of low power consumption.
Preferably, the radiant panel is electroluminescent (EL) material positioned above the contact membrane or printed circuit board and generally below the keyswitch caps. In embodiments in which the EL material comprises strips or a sheet with perforations, the strip edges or perforation edges are disposed on at least two sides of, and preferably entirely or substantially around, the key stem or the space through which the stem travels during depression of the key (xe2x80x9cstem pathxe2x80x9d). In embodiments in which the EL material comprises a continuous sheet of material, the sheet extends generally horizontally underneath a plurality of keyswitches between the contact membrane and the lower-most extremity of the keyswitch. When a key is depressed, the continuous sheet is impacted by the contact member of the keyswitch, and transfers force to the contact membrane to execute the xe2x80x9cswitch.xe2x80x9d Thus, at a minimum, the EL material preferably extends underneath the peripheral edges of the key cap, or at a maximum, the EL material extends all the way under the key, either scenario allowing a significant amount of light to pass into and up through the keyswitches, and preferably also between the spaces between the keyswitches. The panel and EL material preferably do not extend into the interior of the key cap or key stem, and do not interfere with operation or removal of the key.
In this and the following Description and Claims, the terms xe2x80x9ckeyswitch assemblyxe2x80x9d or xe2x80x9ckeyswitchxe2x80x9d or xe2x80x9ckeyxe2x80x9d refer to the device conventionally provided in keyboards that is depressed to make contact with and affect (close) its particular switch on the circuit board or membrane (PCB or contact membrane). A keyswitch is typically made of what is called herein a xe2x80x9ccapxe2x80x9d for finger contact and a xe2x80x9ckey stemxe2x80x9d or xe2x80x9cstemxe2x80x9d which is the generally vertical structure protruding from the cap toward the circuit board or membrane and which contacts the board or membrane when the key is depressed. Thus, xe2x80x9ckey stemxe2x80x9d herein refers to the downwardly-protruding post attached to the cap, plus inserts, sleeves, domes, and biasing members that extend around or are otherwise connected to the post. The cap and stem of a keyswitch may be separate components, or may be a single component plus a biasing member, for example. In the Description and Claims, the term xe2x80x9csubstantially continuous panelxe2x80x9d means that a panel extends without significant apertures or interruptions except for apertures that are used to receive a portion of the keyswitch such as the stem or to reach near to the stem but leave a space for the stem path, that is, for the stem to move in and out of the aperture. The term xe2x80x9ccontinuous panelxe2x80x9d means that the panel extends without significant apertures or interruptions, for example, panels that have no apertures for receiving the keyswitch stems. The inventors envision that a single continuous panel would be beneficial in a laptop computer keyboard that would have no keyswitch stem apertures but would have a hole through the membrane for receiving a xe2x80x9cmouse ballxe2x80x9d mechanism, for example. The term xe2x80x9cextending betweenxe2x80x9d means that a panel extends from keyswitch to keyswitch on any number of planes that are near the keyswitches and generally parallel to the plane of the keyswitches, and is not intended to limit the panel location to one particular plane passing through the midpoint of the keyswitches.
One or more panels comprising EL material may be laid down between keyswitches and around the stems or stem paths or underneath the keyswitches, in one or more areas of the keyboard. The panels may be of various regular or irregular shapes to backlight particular areas of the keyboard, and the panels may radiate light over all or substantially all of their top surfaces, or may have areas masked or deactivated from radiating light so that not all of the panel radiates light. Panels are herein described in two general categories, sheets and strips, wherein a sheet typically extends between more than two rows of keys and/or more than two columns of keys, and a strip typically extends between only two rows of keys or between only two columns of keys. Several different panels may be provided, for easier design and installation, or for being separately-powered for independent on/off or dimming control. Also, EL panels may be used that provide different colors of backlighting, for differentiating different areas of the key board. Also, not all areas of the keyboard need to be lit.
Preferably, the keycaps used with the present invention are molded using translucent plastic and have opaque markings or portions on their tops, and the key stems and other parts of the keyswitches are either translucent, transparent, or reflective, so that the keyswitch as a whole tends to transfer or reflect light. Also, the EL material may be positioned directly underneath a translucent or transparent base plate that is the uppermost portion of the housing of the keyboard. Alternatively, the EL material may be positioned above a base plate, or installed without a base plate. This way, because the EL material preferably extends across substantially the entire distance between keys, and optionally across the entire distance outside and beneath the keys, the EL light travels upward through and around the translucent keycaps and up through the base plate, thereby backlighting selected portions or substantially the entire top of the keyboard, to xe2x80x9cfillxe2x80x9d the keyboard surface with light. Thus, the invented system does not feature only the interior lighting, that is, the limited, controlled xe2x80x9clight pipexe2x80x9d or axially-channeled light approach discussed in the Related Art section. Instead, the invented system produces a subtle, overall lighted effect that yet is not overwhelming or distracting. Having light xe2x80x9cglowxe2x80x9d from between the keycaps as well as from the keycaps is surprisingly effective, and produces a xe2x80x9cplane of lightxe2x80x9d effect, giving the user enough subtle light to see and use the keyboard without having xe2x80x9cspotsxe2x80x9d of light or indicia only lit up on top of the key caps.
The radiant EL panels are preferably powered by the computer keyboard port, via voltage inverters which are commercially available for such use. Preferably, one or more dimming, on/off, and auto-off control systems are included in the invented system. These controls may be used to adjust the intensity of the backlighting in some or all portions of the backlit keyboard. Also, these controls may be used to automatically shut off lighting during extended non-use, for battery conservation, and restart it when one or more keystrokes are made. In addition, the preferred controls may be used to independently dim or turn off the lighting of all or selected portions, for example, to produce increased differentiation between the lit portions and the dimmed or non-lit portions.
The invented backlighting system allows easier key identification for fewer input errors, for example, for late night use without disrupting sleeping family members and use on airplanes. The invented system allows a user to accurately and comfortably use the keyboard after purposely darkening a room to reduce glare and shadows. The overall-lighted keyboard may reduce eye fatigue that otherwise may occur when constantly moving the eyes from a lighted monitor to an un-lit keyboard. The intensity adjustment option gives users the ability to adjust the keyboard lighting for their own personal comfort and room conditions.
Another objective of the invented system is to provide a durable lighting system that results in a durable and low-maintenance keyboard. The invented system may use conventional, solid keyswitches without hollow centers, and does not require hollow key stems or special modifications to keyswitches, except for the preferred change to translucent materials. The invented system does not significantly increase the temperature of the keyswitches. The invented system does not require electronic or other complex connections of lighting members to the keyswitches. The preferred system therefore provides an economical lighting mechanism that does not reduce the reliability and life of the keyboard.
The invented backlighting system utilizes commercially-available lighting members, in such a way as to provide a system of efficient, glare-free and low-cost keyboard illumination. The invented system of lighting can be made into any shape of size, for design into new keyboard assemblies, or retrofitting onto existing keyboards, as will be more fully described in the detailed specification which follows.